Cosmology Definition and 948 Threads

Cosmology (from Greek κόσμος, kosmos "world" and -λογία, -logia "study of") is a branch of astronomy concerned with the studies of the origin and evolution of the universe, from the Big Bang to today and on into the future. It is the scientific study of the origin, evolution, and eventual fate of the universe. Physical cosmology is the scientific study of the universe's origin, its large-scale structures and dynamics, and its ultimate fate, as well as the laws of science that govern these areas.The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia, and in 1731 taken up in Latin by German philosopher Christian Wolff, in Cosmologia Generalis.Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology.
Physical cosmology is studied by scientists, such as astronomers and physicists, as well as philosophers, such as metaphysicians, philosophers of physics, and philosophers of space and time. Because of this shared scope with philosophy, theories in physical cosmology may include both scientific and non-scientific propositions, and may depend upon assumptions that cannot be tested. Cosmology differs from astronomy in that the former is concerned with the Universe as a whole while the latter deals with individual celestial objects. Modern physical cosmology is dominated by the Big Bang theory, which attempts to bring together observational astronomy and particle physics; more specifically, a standard parameterization of the Big Bang with dark matter and dark energy, known as the Lambda-CDM model.
Theoretical astrophysicist David N. Spergel has described cosmology as a "historical science" because "when we look out in space, we look back in time" due to the finite nature of the speed of light.

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  1. marcus

    Interested in Spinfoam Cosmology? Check out Francesca Vidotto's Online Talk!

    Spinfoam cosmology is a fast-growing field, since it represents the application of the full LQG theory to the BB and expanding universe. In the early years loop cosmology addressed a restricted model with just a small number of degrees of freedom. Going from oldfashioned LQC loop cosmology to...
  2. TrickyDicky

    Relativity of simultaneity and cosmology

    According to SR relativity of simultaneity, the temporal order of events depends on the frame of reference from which the observer watches the events and different observers with a spacelike separation between them or at relativistic speeds won't agree in the order of events. Now , in...
  3. A

    How Is Redshift Calculated in Changing Epochs?

    Homework Statement The redshift of a galaxy is measured at the present epoch t0 and again at the infnitesimal future epoch t0 + δt0. Show that the rate of change of z with t0 is given by \frac{dz}{dt_{o}}=(1+z)H_{o}-H(z) Homework Equations Hint - Start From: \frac{\delta z}{\delta...
  4. H

    Studying Topics to be covered before studying cosmology

    I would like to ask what topics one should study before studying cosmology. I have begun self-learning physics since last summer, and my goal is to build a foundation solid enough to learn cosmology in great depth. I seem to be just touching on different topics: relativity, the uncertainty...
  5. K

    PhD in Cosmology: Best UK Universities

    Could anyone suggest good universities in the UK for studying cosmology at a PhD level? Thank you!
  6. G

    What Is the Age of the Universe According to Different Models of Cosmology?

    Homework Statement From CMB measurements, we know the total density of the Universe matches the critical density to 2 percent. From observations of Supernova it seems that 70 percent of that is in the form of dark energy. But the supernova observations are not as solid as the CMB result...
  7. G

    Programs Which UK Universities Offer the Best PhD Programs in Cosmology?

    Hi, I graduate university this summer with a physics degree, (4 year masters, specialising in astrophysics and particle physics), and I'm very keen to do a PhD in cosmology. Does anyone know which departments are the best to work in, for this field? I'd love a project on QSOs as a probe of...
  8. S

    Is a Cosmology PhD a Dead End or a Gateway to Diverse Career Opportunities?

    I've asked a similar question earlier already, but I want to be more specific now. I'm contemplating doing a PhD in cosmology (mainly numerical analysis of galaxy observations). It's a good group with a good international standing. I'm just a bit worried about the time after my PhD. How...
  9. T

    Is the future of Cosmology limitless or are we bound by fundamental questions?

    I have some general, fundermental questions about Cosmology and the future of Cosmology: 1. Is there a resource or management initative of some kind, which is keeping track of all the theories, sub theories, completely different theories and competing theories related to cosmology? If so is...
  10. B

    Question from Weinberg's cosmology text

    I am trying to learn gauge issues in cosmology from Weinberg's "Cosmology". However, I am completely stumped at how he gets 5.3.4 from 5.3.3. I was doing great until that point and now I'm going crazy. Any help would be highly appreciated!
  11. bcrowell

    More on Penrose's Conformal Cyclic Cosmology

    We had a discussion of Penrose's conformal cyclic cosmology last month: https://www.physicsforums.com/showthread.php?t=427567 His popular-level book Cycles of Time was published first in the UK, but is now available in the US. I got a copy and have read it, so I can report on a few of the...
  12. A

    [Cosmology] Fundamental Plane to find distance

    I have been given data for the Coma and S639 clusters, including their velocity distances. For part a I calibrated the fundamental plane using the Coma data, and got: log(Re) = 1.24log(\sigma) - .82log<I> - .259 I am now supposed to use the S639 data along with the above fit to get a distance...
  13. P

    Physics Is a Career in Astrophysics and Cosmology Still Risky in 2010?

    Hello Its 2010 now and I am not really up to date with careers. Is it still an extremely risky to go into astrophysics and/or cosmology? Can you guys tell me how things are going for scientists of all branches if you know? Thanks
  14. marcus

    Bounce derived in spinfoam cosmology

    http://arxiv.org/abs/1010.1258 Big Bounce in Dipole Cosmology Marco Valerio Battisti, Antonino Marciano 5 pages (Submitted on 6 Oct 2010) "We derive the cosmological Big Bounce scenario from the dipole approximation of Loop Quantum Gravity. We show that a non-singular evolution takes place for...
  15. K

    Superstring Cosmology: Compactifying 7 Dimensions

    In Superstring Cosmology and Superstring Gas Cosmology they try to address the question as to how compactification occurs. Is it believed that possibly cosmic strings wrapped themselves around 7 dimensions and collapsed due to their tension? This isn't a personal theory just a curiosity as to...
  16. S

    Exploring Loop Quantum Cosmology with the Planck Satellite

    Will the results from the PLanck satellite shed any light on Loop Quantum Cosmology or any other form of matter bounce?
  17. R

    Cosmology Questions That Have Perplexed Me Over the Years

    Hi all, it's my first post here, and I'm glad to have found it. I'm a software engineer by trade, but I've always been immensely fascinated by cosmology, and I think it's my true passion (when I went to school, I was concerned that pursuing cosmology would not pay the bills, so the pragmatist in...
  18. marcus

    Cycles of time-Penrose says his cyclic cosmology obeys thermodynamics.

    Cycles of time--Penrose says his cyclic cosmology obeys thermodynamics. Roger Penrose has devised a cyclic cosmology which he sees as not violating the second law of thermodynamics. There are several online videos of him lecturing about it. I'll get some links. I'm curious to know if others...
  19. P

    Schools What are the top universities for Cosmology?

    What are the top undergrad universities for a major in Cosmology minus Ivy?
  20. C

    Is Our Understanding of the Universe Shaped by Archetypal Concepts?

    Hello, I've been thinking recently about the truths and realities that are found in the Universe and I just wanted to share a bit of what I have been thinking about. I'm 16 years old right now and I have a drive to understand the way nature displays itself to conscious beings. I'd like to...
  21. marcus

    Chalnoth case against Loop Quantum Cosmology

    Loop Quantum Cosmology could be interesting to discuss because 1) it has been radically transformed since 2007 (with what Ashtekar calls "improved dynamics") 2) it has begun a phase of rapid growth (new crop of researchers , publication rate more than doubled since 2006) 3) it now includes...
  22. S

    Pre Big Bang Cosmology: Is There a Consensus?

    Is there a consesnsus as to whether the big bang represent an ultimate beginning ? it seems to me that the answer to that question is no. The reason for this is that we need a quantum theoy of gravity to describe the moment of the big bang and all current attempts at this eg LQG, Hoyava...
  23. MathematicalPhysicist

    Arithmetic quantum gravity and cosmology

    So basically I am about to embark on my Msc in the pure maths department. Now I wish to conduct research on the subject of arithmetic quantum chaos and its applications in number theory and in gravity and cosmology. In my university I found someone who is an expert in its applications to...
  24. S

    Can Conformal Weyl Gravity be a Viable Cosmology?

    Can Conformal Weyl Gravity be considered a viable cosmological theory?
  25. D

    Need career guidance in cosmology

    Hi All, I am a computer science engineering graduate , currently working in software company. I am very much interested in cosmology since my childhood. I tried putting off my urge to choose cosmology as my career for a very long time. But I can't do that anymore. So can anyone suggest me...
  26. M

    Programs PhD in Cosmology with a 2nd Class Degree

    I am just going into my fourth year of a 4 year MSci course and have got my results from my third year. It's not as good as I had hoped and my average is a 2.1. I know that Cosmology is very difficult to get into and PhD's are over subscribed. I was also hoping to work at one of the...
  27. B

    Is the standard model of cosmology flawed?

    What exactly is going on in physics and with the standard model of cosmology? We had a model that seemed to describe in absolute perfection the workings of the universe, but over the last few decades observations have been made that explicitly counter what's expected from general relativity...
  28. P

    Durham vs Manchester in Astrophysics (Cosmology) - Postgraduate

    Hi all. I have been applying for graduate (research) studies in Astrophysics (I am interested in cosmology - CMB, SNIa, models...) at some UK universities - Imperial College, Durham, Glasgow, Manchester. All of them have research groups in the field of cosmology. So far I have received an...
  29. P

    Books on Cosmology of Stellar Objects

    I have been reading Kip Thorne's marvelous book ""Black Holes and Time Warps" to familiarize myself with general relativity. Along the way, I have found he discusses many fascinating cosmological topics that I would like to explore further. I am looking for books about the various types of...
  30. MathematicalPhysicist

    What are the best resources for studying Quantum Cosmology?

    OK, I have a plan to learn this summer after all of my exams will end, some subjects in physics and maths (GR,QFT, measure theory,DG and some random matrix theory, not sure if this plan is tangible, I'll try), so for GR I think of using Wald's and A First course in GR, maybe I'll also look at...
  31. marcus

    Henderson video: spinfoam approach to cosmology

    Henderson gives a good talk. He's been working with Abhay Ashtekar on reformulating loop cosmology as a spinfoam-like path integral---also using GFT (group field theory) where a parameter shows up that may have physical interest (possible connection with the cosmological constant). He got...
  32. J

    Is Evolution Considered Part of Cosmology?

    Is evolution (Darwinian) considered part of the science of cosmology? or would that be another subject entirely?
  33. L

    Questions on Relativity & Cosmology Regarding Galaxies

    I'm confused a little bit by this and have a few questions. I wasn't sure where to put this because it's kind of a relativity question (time dilation) and a cosmology question combined. From what I understand, all galaxies are moving away from us. But isn't the Andromeda galaxy eventually...
  34. E

    String theory cosmology on inflation, CMB, gravitional waves?

    cosmology strings vs loops How well does string cosmology account for inflation, CMB, gravitational waves, evolution classically using FRW metric? does string cosmology offer either qualitative or quantitative predictions? This paper addresses these in the loop framework...
  35. D

    Curvatue Cosmology for a static stable universe

    Curvature Cosmology is a cosmology based on two hypotheses. The first, curvature redshift, is an interaction between photons and curved spacetime and produces the observed Hubble redshift. It can also explain the anomalous Pioneer 10 acceleration. The second, curvature pressure, is a...
  36. X

    Cosmology or Theoretical Physics for job?

    ¿Cosmology or Theoretical Physics? I have a dilemma. I have an offer for Cosmology and I have an offer for Theoretical Physics. I'm ofcourse aware of both fields, but I would like to know from you what their main differences are. Thank you!
  37. P

    Special Relativity / Cosmology

    2 galaxies are "moving" away from each other due to the expansion of space, if each is moving away at 3/4 the speed of light relative to the other would they not be moving faster than light relative to each other? Is the expansion of space limited to 1/2 light speed ? Does the law of non...
  38. C

    How Does Energy Density Change with Scale Factor in Cosmology?

    Homework Statement The fluid equation in cosmology is given as: \dot{\epsilon} + 3*(\dot{a}/a)*(\epsilon+P) = 0 Where \epsilon is the energy density and a(t) is a scale factor. Using the equation of state, P = w*\epsilon, show how \epsilon change with a(t). Homework Equations...
  39. planethunter

    God & Cosmology: Perceptions & Opinions

    A pretty loaded title for the thread (I know). I would like to know what are everyone's perceptions/opinions regarding the beginning of the universe (of time) as it relates to the notion of a god or God?
  40. O

    Is Gravity Truly an Entropic Force in the Universe?

    Entropic gravity and cosmology The considerable impact of Verlinde’s recent paper in which he suggests that gravity is nothing but an entropic force has familiarised many with this type of force. Verlinde wrote: The examples he mentions involve constituents in thermal equilibrium with...
  41. F

    Theoretical Physics vs Theoretical Cosmology

    What exactly is the difference? The latter does not seem so popular to me? On average how much does the latter earn?
  42. A

    Good Cosmology Books: Recommendations

    Hey! Can you please recommend me some good and up to date cosmology books? Thanks!
  43. Physics Monkey

    Loop Quantum Cosmology: Exploring Physics

    Hi everybody, I would like to chat about the physics of loop quantum cosmology. Let me list a few broad topics I'm interested in understanding better: 1. What simplifications/approximations make loop quantum cosmology a solvable simplification of full loop quantum gravity? 2. How is...
  44. S

    Astronomy, Astrophysics, Cosmology, Planetary Science

    What exactly are the differences between Astronomy, Astrophysics, Cosmology, Planetary Science?
  45. G

    Programs Best Physics PhD Programs in Cosmology?

    What are the best "2nd tier" physics PhD programs known for cosmology? Thanks
  46. Ivan Seeking

    Astronomy or Cosmology Christmas gift ideas

    I have a friend asking for ideas for an A or C oriented gift, including things that might be a bit of a scam, like having a star named after you. I know that you can buy land on the moon but that is expensive. Any ideas?
  47. R

    Cosmology: Horizon of the universe

    Homework Statement This is what the question says exactly: Assume the universe today is flat with both matter and a cosmological constant but no radiation. Compute the horizon of the Universe as a function of \OmegaM and sketch it. (You will need a computer or calculator to do this).Homework...
  48. C

    How Far Could Light Travel by the Time of Decoupling in an Expanding Universe?

    Homework Statement At the time of decoupling the universe was 1/1000 of its present size. How for could light have traveled in the time up to decoupling? (assume that the universe was dominated by radiation until then) Homework Equations The Attempt at a Solution I'm a little...
  49. A

    Does University Reputation Impact PhD Admissions in Cosmology?

    So, I'm interested in the big questions. I guess that leads me towards cosmology - though, quantum or particle physics, or string theory are also tied to the stuff that I want to find out. I'm doing my BS in physics right now and I'm trying to figure out where I want to go for the PhD. I...
  50. B

    Cosmology inequality that I'm struggling to make sense of

    My lecturer has written the following:Given \frac{4 \pi \rho a^3 c^2 }{3} and V = \frac{4 \pi a^3}{3} , then substituting \frac{dE}{dt} = -p\frac{dV}{dt} we have: \frac{d(\rho a^3)}{da} = -\frac{3pa^2}{c^2} \leq 0 (1) Ok that part is fine - substitute and use the chain rule: So, if we...
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